This invention relates to the method for reducing corrosion in refined hydrocarbon fuels by removing elemental sulfur from said fuel. More particularly, this invention involves an improved method of reducing corrosion in refined hydrocarbon fuels by adding an organo mercaptan compound and a copper compound capable of forming a soluble copper complex with any mercaptan and elemental sulfur present in the fuel and contacting said fuel with an adsorbent material to remove the copper complex and substantially all of said elemental sulfur.
The problems associated with the presence of sulfur compounds, and particularly elemental sulfur and mercaptans, in hydrocarbon fuels has been known for a long time. Various techniques have been developed for removing said sulfur materials from hydrocarbon compositions. Such techniques include a process for treating petroleum oil by passing vapors through a mixture of an anhydrous silicate and a salt of a metal having an affinity for the sulfur compounds of the oil (such as malachite, azurite or cuprite) as disclosed in U.s. Pat. No. 1,587,491 issued to R. Cross on June 1, 1926. Another patent to R. Cross, U.S. Pat. No. 1,840,158 issued on Jan. 5, 1932 discloses a two-stage process for sulfur compound removal from light hydrocarbons wherein the first stage comprises treating the hydrocarbons under pressure in vapor phase with a metallic compound such as copper or other metal having an affinity for sulfur and then through a subsequent treating zone comprising a solid adsorbent material such as clay. U.S. Pat. No. 2,028,995 issued to F. M. Rogers on Jan. 28, 1936 discloses a process for desulfurizing petroleum oils using solid adsorbent catalytic materials of the clay type at high temperatures to convert difficult to remove sulfur compounds into easily removable sulfur compounds, U.S. Pat. No. 2,276,526 issued to G. H. von Fuchs et al on Mar. 17, 1942 discloses a process for removal of mercaptans without forming disulfides as well as removal of disulfides originally present by treatment with cuprous oxide. U.S. Pat. No. 2,496,536 issued to C. O. Hoover on Feb. 7, 1950 discloses a process in which elemental sulfur and sulfur compounds such as mercaptans, bisulfides, sulfides and hydrogen sulfide are removed from petroleum distillates by contacting vapors with the copper salt of an alkyl or aromatic carboxylic acid, such as copper naphthenate. Another technique is disclosed in U.S. Pat. No. 2,768,932 issued to G. P. Richard et al on Oct. 30, 1956 and involves a process for the further desulfurization of hydrofined petroleum distillates by treating said distillates in vapor phase with finely divided metallic copper, copper containing alloys or cupric oxide. U.S. Pat. No. 3,378,484 issued to J. M. Ferrara et al. on Apr. 16, 1968 discloses a method for removing mercaptans from liquid hydrocarbons by bringing the hydrocarbons into contact with a finely divided particulate ion exchange material containing a metallic element such as copper, mercury, silver, lead, iron etc.
The above-noted patents all disclose the well known desirability of removing sulfur compounds from petroleum hydrocarbons and one of the techniques for accomplishing this involves contacting the hydrocarbon composition with a metallic compound such as copper. Now it has been found that the amount of elemental sulfur and corrosion in refined hydrocarbon fuels can be significantly reduced when small effective amounts of organo mercaptan compounds are added to the fuel in combination with a copper compound capable of forming a soluble copper complex with any mercaptan and elemental sulfur present in the fuel. The sulfur and complex are removed in a subsequent step wherein the fuel is contacted with an adsorbent material.
This method wherein mercaptan compound is added to the fuel composition is somewhat contrary to the generally known techniques which indicate the necessity to remove mercaptan from the fuel and do not suggest the addition of a mercaptan to aid in removal of elemental sulfur.